“…During operation, almost all of them faced the problem of tar removal. Although attempts have been made to remove tar from the product gas using a spray column (Cruz, 1980), an oil venturi (Graboski and Brogan, 1988), fabric filters (Khummongkol, 1989), packed bed filters made from rice husk (Khummongkol, 1989), an electrostatic precipitator (Nonhebel, 1964), gas impingement on a water surface (Khummongkol, 1989), and a bubble cap 0363-907X/92/08073 1 -1 1 $10.50 0 1992 by John Wiley & Sons, Ltd.…”